Proc. Nat. Acad. Sci. USA Vol. 69, No. 9, pp. 2645-2648, September 1972 Thiolester Substrates for Transamidating Enzymes: Studies on Fibrinoligase (acyl group transfer/hydrolysis/transglutaminase/Factor XIII) L. LORAND, C-H. J. CHOU, AND I. SIMPSON Biochemistry Division, Department of Chemistry, Northwestern University, Evanston, Illinois 60201 Communicated by Irving M. Klotz, July 10, 1972 ABSTRACT Esters of thiocholine were shown to in- MATERIALS AND METHODS hibit the crosslinking of fibrin clots by the transamidating enzyme, fibrinoligase (thrombin-activated fibrin-stabiliz- The fibrinoligase zymogen (i.e., Factor XIII or fibrin-sta- ing factor or activated Factor XIII). Inhibition depended bilizing factor) was isolated from 6 liters of bovine plasma by on the nature of the pcylating group with the phenylpro- DEAE-cellulose chromatography and elution with a salt pionyl, phenylbutyryl, and trans-cinnamoyl esters being most effective of the compounds tested so far. gradient (5). The concentrate of active fractions was then Use of the thiolesters made it possible for the first time filtered through a 3 X 90 cm Agarose A-0.5 (Biorad, Rich- to study the reactions of fibrinoligase in fully synthetic mond, Calif.) column in Tris-EDTA buffer [0.05 M Tris- substrate systems. Enzyme-catalyzed acyl-group transfers HC1 (pH 7.5) containing 1 mM EDTA]. Fractions of high from the thiol-esters to a fluorescent amine [N-(5-amino- activity were pooled and concentrated by passage pentyl) - 5 - dimethylamino- 1- naphthalenesulfonamidel through could be readily demonstrated and measured. a 0.9 X 7 cm DEAE-cellulose column at high ionic strength Trans-cinnamoylthiocholine reacted with fibrinoligase (0.3 M sodium chloride in Tris-EDTA buffer) and dialyzed in a totally calcium-dependent manner in the absence of against the Tris-EDTA buffer to remove sodium chloride. any added amine, thus providing the first evidence for an The purified zymogen was stored as such in ice. Its potency, esterolytic pathway for this enzyme. Spectral qualities, as well as appreciable extent of solubility in water, would after thrombin activation, was monitored by the incorpora- seem to make trans-cinnamoylthiocholine a specially tion of [14C]putrescine (54 Ci/mol) into casein with the filter- suitable substrate for further studies. paper assay recently developed in this laboratory (6). The preparation was stable for at least 6 weeks. Protein concen- Fibrinoligase, a thiol enzyme similar in many respects to trations were computed on the basis of an assumed absorbancy papain or to liver transglutaminase, is formed at the time (1%, 280 nm) of 15. of coagulation by the limited proteolytic action of thrombin Inhibition of fibrin crosslinking was evaluated with only on a zymogen component of blood plasma (called fibrin- minor modifications of the monochloroacetic acid clot-sol- stabilizing factor or Factor XIII). Its physiological role is ubility assay (2). Activation of 0.4 ml of the Factor XIII to catalyze the crosslinking of fibrin units by a selective trans- zymogen (0.3 mg) solution was performed at room temper- amidation reaction, producing intermolecular y-glutamyl-e- ature (22-24°) by incubation with 0.1 ml of 50 mM calcium lysine bridges that greatly enhance the elasticity of the clot chloride and 0.2 ml of thrombin (Parke-Davis, 4 NIH units) structure. The functioning of fibrinoligase appears to be for 10 min. Then, 0.5 ml of the inhibitor solution was added, absolutely essential for normal hemostasis (for a review, see followed 10 min later, by admixture of 0.3 ml of a 0.6% fibrin ref. 1). solution, producing an almost instantaneous gelation. After Previous accounts from this laboratory dealt rather ex- 30 min 1.5 ml of 2% monochloroacetic acid was added in an tensively with the amine-donor substrate specificity of the attempt to solubilize the clot overnight. Insoluble or cross- enzyme. This could be studied by inhibition of fibrin cross- linked clot residues were separated by centrifugation and linking and by the kinetics of amine incorporation into fibrin washed twice with 10 ml of 0.9% sodium chloride and twice or casein. Several synthetic primary amines, especially those with water. The washed proteins were taken up in 2.5 ml of a containing an aliphatic tetra- or pentamethylamine side mixture of 40%O urea and 0.2 N sodium hydroxide for measure- chain analogous to the e-NH2 lysine natural donor groups in ment of absorbancy at 280 nm. fibrin, were particularly effective (2-4). The calcium chloride, thrombin, and inhibitor solutions The present report is directed towards the exploration of were prepared in 0.05 M Tris *HC1 (pH 7.5). Control clotting acceptor specificity with model substrates in the thiolester mixtures contained potassium iodide in equal concentrations series. Apart from acting as inhibitors of the biological cross- to the inhibitors used. Fibrin was dissolved in 1 M sodium linking of fibrin, these compounds now make it possible to bromide and the pH of the solution was adjusted to 5.3 with study acyl transfers to amines as well as hydrolytic reac- acetic acid (7). tions with fibrinoligase in fully synthetic systems. Trani- cinnamoylthiocholine is of special interest as a substrate Thiocholine iodide was purchased from Polyscience (War- because of the spectral changes that accompany its reactions rington, Pa.); acetylthiocholine chloride and iodide, and with the enzyme. butyrylthiocholine chloride and iodide were purchased from Sigma Chemical Co., St. Louis, Mo.; propionylthiocholine Abbreviation: monodansylcadaverine, N-(5-aminopentyl)-5-di- iodide was obtained from Mann Res. Lab., New York, N.Y. methylamino-1-naphthalenesulfonamide. Phenylpropionyl-, phenylbutyryl-, benzoyl-, trimethylacetyl-, 2645 Downloaded by guest on September 26, 2021 2646 Biochemistry: Lorand et al. Proc. Nat. Acad. Sci. USA 69 (1972) -TABLE 1. Inhibition of the enzymatic crosslinking offibrin by esters of the thiocholine series [RCOSCH2CH2N(CH3)3I-J* Inhibitory potencyt R group (M-1) CH3 15 ~0 CH3CH2 29 (CH3)3C 37 I1- CH$CH2CH2 46 C6H5 527 I4ropionyl, C.H6CHCH 714 or JTnmethylacetyl, I- C6HCH2CH2 CsH6CH2CH2CH2 910 * (see Fig. la and b). t Inhibitory potency is defined as the reciprocal of the initial Butyryl concentration of the compound that causes 50% reduction in the * *-roiny, A amount of crosslinked (i.e., monochloroacetic acid-insoluble) clot. CI- 0 2 4 6 8 [R-Thiochoin], M X 10 to take place for 10 min at room temperature, then 5 MuI of 3 mM monodansylcadaverine and 30 ul of thiolester solutions (to yield the concentrations specified in the text) were added, b and the reaction mixture was incubated at 37°. At various times, 1-1A aliquots were taken and spotted onto a thin-layer chromatographic plate (Brinkman Polyamid) and dried immediately by exposure to air current. Consecutive samples were applied 1.5-cm apart and the plate was developed by ascending chromatography in 1% pyridine adjusted to pH 5.4 with acetic acid. The positively charged monodansyl- cadaverine substrate moved with the solvent front (8), whereas the uncharged monodansylcadaverine derivative I ~~A stayed at the origin. Disappearance of substrate and appear- ance of the product were quantitated by fluorescence reflec- tance scanning with a Turner model 111 Fluorimeter, as described (8). #-Oropionyi- t-Cinnamoyl 3min 6min 0.5 1.5 2.5 3.5 [R-TNocholine]0, M K 103 FIG. 1. (a and b) Specificity of inhibition of the enzymatic crosslinking of fibrin by thiocholine esters containing various acylating (R) groups. For methodology, see text and ref. 2. 10 mmn Potassium iodide, potassium chloride, and thiocholine iodide (<10 mM) showed no inhibition. In Fig. lb, only the iodide P salts of thiocholinium esters were used. Inhibition by phenyl- butyrylthiocholine (not shown) was indistinguishable from that caused by the phenylpropionyl ester. 20 min and trans-cinnamoylthiocholine iodides were synthesized in this laboratory. N-(5-Aminopentyl)-5-dimethylamino-l-naphthalenesulfon- FIG. 2. Fluorescence reflectance scans after analysis by thin- amide or "monodansylcadaverine" (2) (gift from Kabi, Stock- layer chromatography of samples (taken at the times indicated holm) was used as donor for the study of enzymatic acyl after addition of enzyme) from a reaction mixture initially con- taining 0.2 mM monodansylcadaverine and 40 mM acetylthio- transfers with thiocholine ester substrates. Reaction mixtures cholinium iodide. P (product) denotes the uncharged fluorescent (in 5 X 25 mm Pyrex tubes) were 20 ,l of 50 mM calcium species remaining near the point of application. Complete con- chloride, 10 ,4l of the Factor XIII zymogen solution (15 ug), version to product was observed in 45 min. For methodology, and 10.ul of thrombin (0.2 NIH units). Activation was allowed see text and ref. 8. Downloaded by guest on September 26, 2021 Proc. Nat. Acad. Sci. USA 69 0972) Thiolester Substrates for Transamidating Enzymes 2647 10 15 Butyrylthidchoine, M x 103 FIG. 3. Reaction between butyrylthiocholinium iodide (in- itial concentrations on abscissa) and monodansylcadaverine 250 275 300 325 350 (0.2 mM added), as measured by the formation (in 20 min) Woveegh, mn of the fluorescent product remaining near point of application on thin-layer chromatographic analysis (see Fig. 2). Net enzymatic rates (A) were obtained by substraction of nonenzymatic values FIG. 4. Spectral analysis of the trans-cinnamolythiocholine- (0) from those measured in the presence of fibrinoligase (e). fibrinoligase system. A. Spectrum of trans-cinnamoylthiocholine (44 uM) and fibrinoligase (65 ag/ml) incubated for 85 min in the presence of calcium chloride (4 mM), taken against a mixture of Spectroscopic experiments with trans-cinnamoyl thio- trans-cinnamoylthiocholine without any calcium chloride added. choline iodide were performed in a Cary 16 Spectropho- (For absorbancy scale, see ordinate on left). B. Trans-cinnamoyl- tometer at 250 in thiocholine (44 uM) in 0.05 M Tris buffer (pH 7.5). (Right semi-microcuvettes with a 10-mm light path.